Before an intervertebral implant is inserted into the intervertebral disc space of a patient, there is often the need to assess the adequacy of the disc space and the implant by first inserting a trial device into the disc space.
Currently, no conventional trial system allows for determination of the angle of the implanted trial following its satisfactory placement and imaging.
US Patent Publication No. 2012-0035730 (Spann) discloses a method for introducing a spinal disc implant into an intervertebral space of a subject. The subject is placed in a lateral position, and the anterior face of the spinal disc intervertebral space is accessed, between the L5 and S1 vertebrae, from an anterior and lateral retroperitoneal approach. An operative corridor to the anterior face of the spinal disc space is established by introducing a retractor instrument anterolaterally to the spinal disc space between the anterior superior iliac spine and the anterior inferior iliac spine. The damaged spinal disc contents are removed from the intervertebral space through the operative corridor, and the implant is advanced into the intervertebral space at an oblique angle and pivoted to position the implant substantially laterally within the intervertebral space. Elongated retractor and insertion instruments, as well as a modified disc implant, are also disclosed for carrying out the method. See Spann at FIGS. 13-14.
US Patent Publication No. 2011-0009970 (Puno) discloses a system for implanting an inter-body device between adjacent vertebrae comprises an inter-body device having a plurality of cans secured to a flexible bridge and having a relief portion therebetween. An inserter tube and complementary bullnoses are advantageously secured to the vertebrae by an extension arm for securing the assembly precisely in place. A plurality of articulating trial implants are provided to test fit a disc space for the proper sized inter-body device.
US Patent Publication No. 2011-0319998 (DePuy Spine) discloses a polyaxial trial suitable for use in lateral approaches. In particular, it discloses a method comprising the steps of: a) laterally inserting a variable-angle trial into an intervertebral disc space, b) determining an angle set by the trial in the disc space, c) providing the angle to an implant-inserter apparatus, d) inserting the implant into the disc space at the angle.
US Patent Publication No. 2006-0229627 (Hunt) discloses an instrument for use in a procedure for inserting a spinal implant between human vertebrae may include a shaft and an end member. The end member may rotate with respect to the shaft. An angle of the end member with respect to the shaft may be varied when the end member is in a disc space between the human vertebrae. The instrument may include a slide for securing the end member at selected angles relative to the shaft. The end member may be separable from the shaft when the end member is in a selected orientation with the shaft. An instrument kit may include a shaft assembly and modular end members for various steps in a surgical procedure, such as disc space preparation, disc space evaluation, and spinal implant insertion. See in particular Hunt at paragraph [0016] and claim 9.
US Patent Publication No. 2008-0077241 (Nguyen) discloses a method of preparing a pair of adjacent vertebral endplates, involving a surgical instrument having a pivoting distal removable insert, a proximal handle portion, a body portion, and a linkage member positioned between the insert and the proximal handle portion, the insert having a first angular position relative to the body. A leading end of the insert may be placed in a first position between two adjacent vertebral endplates and moved to a second position between the adjacent vertebral endplates by impacting the proximal end portion of the surgical instrument. The insert may be pivoted to a second angular position relative to the body portion by rotating the handle about the body portion and may lock the second angular position of the distal insert. The insert may be moved to a third position between the adjacent vertebral endplates by impacting the proximal end portion of the surgical instrument.
US Patent Publication No. 2008-0065082 (Chang) discloses instruments and methods for inserting a rasp into an intervertebral space of a spine and using the rasp to decorticate the adjacent vertebra. More particularly, one embodiment provides an instrument that actively changes the angle of the rasp relative to the instrument. The delivery instrument may use a gear portion to articulate the rasp. A second gear on the rasp may mate with a corresponding gear on the instrument. As the instrument gear rotates relative to the instrument, the instrument gear drives the rasp gear, thereby rotating the rasp to decorticate the vertebra. Trial inserts and methods are also provided to determine an appropriate size of a rasp for decortication.
US Patent Publication No. 2008-0140085 (Gately) discloses a method to insert a spinal implant into a vertebral space, the method including the steps of: grasping the implant with a distal end of an implant insertion tool; holding a proximal end of the implant insertion tool and inserting the implant toward the vertebral space; and manipulating the proximal end to apply a yaw movement to the implant while the implant is attached to the tool and in the vertebral space.
US 2012-0277877 (“Smith”) discloses an intervertebral spacer and an insertion tool providing multiple angles of insertion.
Adjustable TLIF implant inserters are limited in angulation to the axial plane for posterior approach surgeries. These devices do not measure the amount of angulation instilled in the trial. Therefore, there remains a need for adjustable trials that allow for flexion of angles of insertion and measurement of the insertion angle for a lateral trial.
In sum, none of the prior art documents discloses a polyaxial trial for anterior, posterior, transforaminal or anterolateral approaches.